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The time series in the bottom plot is the product of the time series in the first and fourth plots.

The sum of two sinusoids

Once again, this time series is the sum of two sinusoids. The frequency of one is the difference between the two original frequencies. The frequency of theother is the sum of the two original frequencies.

However, in this case, the difference frequency is not zero . Rather, it is a very low frequency. What you see in the bottom plot of Figure 1 is a sinusoid whose frequency is the sum of the two original frequencies addedto a sinusoid whose frequency is the difference between the two original frequencies. Because the two original frequencies were almost equal, thefrequency of the second sinusoid is very low.

As you can see, the low-frequency component in the bottom plot in Figure 1 appears to be the beginning of a cosine function whose period is much greaterthan the width of the plot (400 points).

Another view of the same data

Figure 2 shows another view of the bottom two plots from Figure 1 .

Figure 2. Products of sinusoids.
missing image

The difference between Figure 2 and Figure 1 is that while Figure 1 shows only 400 points along the x-axis, Figure 2 shows 1200 points along the x-axis. Thus, the horizontal scale in Figure 2 is significantly compressed relative to the horizontal scale in Figure 1 .

More than one cycle

Figure 2 lets you see a little more than one full cycle of the low-frequency component of the time series produced by multiplying the two sinusoids.

( Figure 2 does not provide a very good representation of the high-frequency component. This is because I plotted 1200 points in a part ofthe screen that is only 400 pixels wide. On my computer, I can expand this to the full screen width. However, I can't publish it at that width, so Ipublished the 400-pixel version.)

Averaging can be problematic in this case

Later on, we will compute the average value of the time series represented by the bottom plot in Figures 1 and 2. Ideally, that average value will be zero.However, you have probably already figured out that a great many data points must be included in the computation of the average to get anything near zero. Aneyeball estimate indicates that about 900 data points are required just to include a single cycle of the low-frequency component.

More examples of the products of sinusoids

Figure 3 shows two additional time series created by multiplying sinusoids.

Figure 3. More products of sinusoids.
missing image

The arrangement in Figure 3 is the same as in Figure 1 . The top plot in Figure 3 is the same sinusoid shown in the top plot of Figure 1 . This is a sinusoid with 32 samples per cycle.

Immediately below the top sinusoid in Figure 3 is another sinusoid. This sinusoid has 24 samples per cycle. As you can see, the frequency of thissinusoid is a little higher than the frequency of the sinusoid in the top plot.

The time series in the third plot down from the top is the product of the time series in the top two plots. Again, this time series is composed of two newsinusoids whose frequencies are the sum of and difference between the two original frequencies.

Questions & Answers

find the 15th term of the geometric sequince whose first is 18 and last term of 387
Jerwin Reply
The given of f(x=x-2. then what is the value of this f(3) 5f(x+1)
virgelyn Reply
hmm well what is the answer
Abhi
how do they get the third part x = (32)5/4
kinnecy Reply
can someone help me with some logarithmic and exponential equations.
Jeffrey Reply
sure. what is your question?
ninjadapaul
20/(×-6^2)
Salomon
okay, so you have 6 raised to the power of 2. what is that part of your answer
ninjadapaul
I don't understand what the A with approx sign and the boxed x mean
ninjadapaul
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
Salomon
I'm not sure why it wrote it the other way
Salomon
I got X =-6
Salomon
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
ninjadapaul
oops. ignore that.
ninjadapaul
so you not have an equal sign anywhere in the original equation?
ninjadapaul
hmm
Abhi
is it a question of log
Abhi
🤔.
Abhi
Commplementary angles
Idrissa Reply
hello
Sherica
im all ears I need to learn
Sherica
right! what he said ⤴⤴⤴
Tamia
hii
Uday
what is a good calculator for all algebra; would a Casio fx 260 work with all algebra equations? please name the cheapest, thanks.
Kevin Reply
a perfect square v²+2v+_
Dearan Reply
kkk nice
Abdirahman Reply
algebra 2 Inequalities:If equation 2 = 0 it is an open set?
Kim Reply
or infinite solutions?
Kim
The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
Al
y=10×
Embra Reply
if |A| not equal to 0 and order of A is n prove that adj (adj A = |A|
Nancy Reply
rolling four fair dice and getting an even number an all four dice
ramon Reply
Kristine 2*2*2=8
Bridget Reply
Differences Between Laspeyres and Paasche Indices
Emedobi Reply
No. 7x -4y is simplified from 4x + (3y + 3x) -7y
Mary Reply
how do you translate this in Algebraic Expressions
linda Reply
Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
Crystal Reply
. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
Chris Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
China
Cied
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
AMJAD
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
AMJAD
what is system testing
AMJAD
what is the application of nanotechnology?
Stotaw
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
Azam
anybody can imagine what will be happen after 100 years from now in nano tech world
Prasenjit
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
Azam
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
Prasenjit
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
Damian
silver nanoparticles could handle the job?
Damian
not now but maybe in future only AgNP maybe any other nanomaterials
Azam
Hello
Uday
I'm interested in Nanotube
Uday
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
Prasenjit
can nanotechnology change the direction of the face of the world
Prasenjit Reply
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
Ali Reply
the Beer law works very well for dilute solutions but fails for very high concentrations. why?
bamidele Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Digital signal processing - dsp. OpenStax CNX. Jan 06, 2016 Download for free at https://legacy.cnx.org/content/col11642/1.38
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